House electric



Aug. 25, 1925. 1,551,295

G. H. FLETCHER DYNAMO ELECTRIC MACHINE Filed Dec. 1, 1924 2 Sheets-Sheet 1 ,26 27 Y 24 I 1" Z l, 26

WITNESS s: INVENTOR V M/ Geo/'yef/fiezcbef.

' Aug. 25, 1925. 1,551,295

G. H. FLETCHER DYNAMO ELECTRIC MACHINE Filed Dec. 1, 1924 2 Sheets-Sheet 2 WITNESSE INVENTOR /f// W Geo/ye /7./7eZ,cfie/r ATTORNEY Patented Au 25', 1925..

UNITED STA-ms] 1,551,295 PATENT A oFF cE.

GEORGE HERBERT FLETCHER, OF. SHEFFIELD, ENGLAND, ASSIGNOR T0 WESTING- nous]: ELECTRIC VANIA.

a mncracrunme company, A conroaarron or PENNSYL- r r l DYNAMO-ELECTBIC momma Application filed December 1, 1924. Serial No. 753,152. I

To allwhomz'tnwy comer n:

Be itknownthat I, GEORGE FLETCHER, a subject of the King offireat Britain, and a resident of Shefiield, in the county of York, England, have inv ted "a new, and useful Improvement in' ynamo-Electric Machines, of which the following is a specification. I

This invention relates to dynamo-electric machines of the totally enclosed type, that is to say, machines wherein the working parts such as the field magnets and armature windings, the brush gear an co-operating rotating pants and the rotor bearings are completely enclosed by means of end bells or other encasing members.

The principal object'of. the invention is to provide an improved air cooling system for such machines whereby efiicient cooling may be obtained without the admission of air from the exterior to the enclosed Working parts.

According to the invention, the cooling air 'is passed through passages in the rotor which communicate with inlet and outlet openings located within the bearings, that is, to say, openings formed in the shaft or end portions of the rotor which project beyond the bearings, and the air passing through the passages in the rotor is prevented from entering the enclosed space containing the working parts of the machine, such as windings, commutator and brushes. In addition, the yoke or frame of the machine, or the exterior portion of the punchings in the case of a machine withskeleton-ty e frame, may be cooled by the provision o ,one or more passages through which cooling air is passed. Preferably, the yoke or frame is jacketed and is provided with projecting ridges which divide the jacket into a plurality of channels and increase the cooling surfaces, and according to a further feature of the invention the yoke or frame of the machine is cast with relatively thick single or multiple helical ridges which provide ducts or channels providing long and restricted pathsrand a consequent high velocity for the cooling air. At the same time, said helical ridges increase the strength of the yoke or frame and add to the volume of magnetizable material therein. The cooling air may be passed through the rotorand throughthe jacket on the yoke or frame either in series or in tecting frame orcasing.

parallel and for this purpose a fan may be employed which is advantageousl mounted upon the rotor and enclosed wit in a pro- 7 According to one arrangement, the fan may be located at one end of the machine so that 1t either draws, or forces air first through the air jacket and then through the rotor in series. According toanother arrangement, the air may enter both the rotor and the yoke jacket at one end of the machine and be drawn therethrough in parallel by means of a fan located at the other end of the machine. According to a further arrangement, the air may be drawn through the rotor and then forced through the yoke jacket after passing through the fan.

To enable the invention to be clearly understood it will now-be described by way of example with reference to the accompanying drawing, where1n'- Figure l is an elevation, partly in section, of a direct-current machine having an air cooling arrangement in accordance with the invention. i

Fig. 2 is a sectional elevation of part of the yoke, showing a modification of my invention.

Fig. 3 is a section on the line III-III of Fig. 2, and

, Figs. 4 and 5 are views similar to Fig. 1 illustrating other modifications of my invention. v

Referring to Fig. l of the drawing, the machine therein illustrated comprises a field magnet system, one pole 1 of which is shown connected to a substantially c lindrical yoke 2, an armature 3 having a p urality of slot conductors 4 and a commutator 5 which cooperates with collector bi-ushes 6. The arma ture 3 rotates in bearings which are enclosed as shown, and comprises the usual slotted core which may be mounted directly on the shaft or as shown upon a spider 8 which in turn is mounted on a shaft 9. Upon the ends of the shaft 9 are mounted cylinders 10 and 11, a spacing cylinder 12 being interposed as shown between the cylinder 10 and the spider 3. The cylinder 10 may be the usual commutator spider. The cylindrical provided between the windings 4 and the cylinders 10, 11 and 12, the arrangement being such that the field magnets, the armature windings and the commutator and brushes are totall enclosed, namely by the yoke 2 and the en bells l3 and 13, the bearing covers, the outer surface of the cylinders 10, 11 and 12 and also the axial vent ducts in the armature, core or spider.

The cylinders and 11 project beyond the ring bearings and are provided with longitudinal passages 15 and l6 respectively, the cylinder 12 being similarly provided with longitudinal passages 17, and the arrangement being such that passages are formed through the length of the rotor through which coolingair can pass without being admitted to the above-mentioned space containing the poles l, armature windings 4, commutator 5 and brushes 6.

A fan 18 of any convenient type is 1nounted upon the commutator end of the shaft 9,

' being preferably protected by means of a casing 19. The said fan is arranged to draw air longitudinally through the passages 16, the rotor spider 8 or armature core vent ducts and the passages 17 and 15.

In the arrangement shown in Fig. 1, the yoke 2 is provided with a helical ridge or thread 20 and is enclosed in an external casin 21 so that a helical jacket space or channel 22 is provided. The jacket space 22 is furnished with an air inlet 23 and an outlet 24:. An air-tight cover 25 is provided at the i the outlet opening 24 of the jacket 22 in communication with the rotor passage 16. The fan 18 thus draws air through the yoke jacket and through the rotor in series.

Thus the circulating external air cools the surfaces of the machine parts along which it passes and also withdraws heat from the enclosed air by passing along relatively thin metallic wall portions constituting part of the enclosure.

With the arrangement above described, it will be appreciated that by reason of the helical ridge or thread 20 which is relatively thick and may be sin le' or multiple, the channel 22 is long an offers an extended cooling surface and a restricted path for the air, resulting in a consequently high air velocity. At the same time the threads 20 increase the mechanical strength of the yoke 2 and add to the volume of magnetic material therein. As previously set forth, the air passing through the rotor and the jacket efliciently cools the enclosed working parts of the machine without coming into contact with the latter. 1

Instead of the helical ridges 20 illustrated in Fig. 1, longitudinal ridges 26 may be employed as illustrated in Figs. 2 and 3, providing a plurality of Ion tudinal air passages 27 and a plurality o openings 23 and 24, and the jacket cover 21 bein provided similar to those previously descri d.

While in the arrangement? shown in Fig. 1 the air is drawn through the rotor and jacket in series, according to the modified arrangement illustrated in Fig. 4 the cooling air is drawn through the rotor and the jacket in parallel. The fan 18 is arranged at the opposite" end of theshaft so that during its rotation it draws air simultaneously through the openings 24 in the jacket and from the passages 16 in the rotor. In this modification, the airpasses in the same direction through the jacket as that described in Fi 1 but in the reverse direction throng the rotor, as clearly shown by the full-line arrows.

In some cases, means may be provided for circulating the air about the totally enclosed working parts. Thus, an auxiliary fan 28 may be provided upon the rotor at the right hand end thereof within the end bell 13 as clearly shown in Fig. 4, a cylindrical liner 29 being provided within the yoke 2 and spaced therefrom so as to provide a substantially cylindrical passage or jacket space 30. With this arrangement, the fan draws air through the air gap between the magnet poles from left to right, and returns it from right to left through the passage or the jacket space 30 as shown by the dotted arrows. Thus, the air circulated by the fan 28 extracts heat from the hot surfaces of the enclosed workin parts and is then cooled by bein broug t into contact with the surfaces w 'ch are cooled by the external air circulated by means of the fan 18.

' It will be understood that various modifications may be made without departing from the scope of the invention. For example, the cooling air may be passed through passages formed in the rotor, or through the commutator spider and the rotor spider, the rotor being so constructed in both cases that the air passing through it cannot enter the enclosed space containing the working parts of the machine.

In Fig. 5, 18 shown a modification of my invention wherein the enclosed air is circulated through a system of special cooling pipes 31 which are in turn cooled by the circulation of the external cooling air.

I claim as my invention:

1. A dynamo-electric machine comprising a stator, a rotor disposed within said stator, said rotor comprising a m etic core, hollow cylindrical members axia y extending on bothQsides of said core and constituting an axial channel extending throughout the entire length ofsaid machine, end members enclosing the ends of said stator, said hollow c lindrical members being journaled in said end members and cooperating therewith to provide a substantially sealed enclosure of the space between the stator and the rotor, and a common means for circulating a cooling medium through said axial channel and along the outer surface of said stator.

' 2. A dynamo-electric machine comprising a stator, a rotor disposed within said stator, said rotor comprising a magnetic core,- hollow cylindrical members axially extending on both sides of said core and constituting an axial channel extending throughout the entire length of said machine, end members enclosing the ends of said stator, said hollow cylindrical members being journaled in said end members and providing a substantially sealed enclosure of the space between the stator and the rotor, means for circulating the air enclosed in said chamber, and means for circulating the exterior air through said axial channel and around the outer surface of said stator.

3. A dynamo-electric machine compris ing a stator member provided with totally terminating outside of bot enclosing end bells, a bearing member carried by each end bell, a rotor member mounted in said'bearing members, the space between said stator member and said rotor member being substantiall hermetically sealed by said bearing mem ers, said rotor; member being provided with an axial passage open to the external air but not to said totally enclosed space, said axial passage extending through the rotor portions which are engaged by both bearin members and of said end bells, an external casing surrounding said stator member and terminating in an airtight cover at one end of the machine, said cover being spaced from the end bell at its end, and means for circulating air through said axial passage and through the spaces provided by said external casing and cover.

In testimony whereof, I have hereunto subscribed my name this third day of October, 1924. GEORGE HERBERT FLETCHER. 

